Field of the Invention
The present invention relates to a technique of control by a control apparatus for an internal combustion engine, for controlling a variable intake cam phase mechanism and a variable exhaust cam phase mechanism which change an intake cam phase and an exhaust cam phase, respectively, when there has occurred a failure state of one or more of the variable intake cam phase mechanism and the variable exhaust cam phase mechanism.
Description of the Related Art
Conventionally, there is known a control apparatus for an internal combustion engine, which is disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2012-31741. The engine is provided with a variable intake cam phase mechanism and a variable exhaust cam phase mechanism of a hydraulically-driven type. In the variable intake cam phase mechanism, the intake cam phase, which is a phase of the intake cam with respect to a crankshaft of the intake cam for opening and closing an intake valve, is changed between a predetermined most advanced value and a predetermined most retarded value, as supply hydraulic pressure from an intake-side hydraulic control valve is changed.
Further, in the variable exhaust cam phase mechanism, the exhaust cam phase, which is a phase of the exhaust cam with respect to a crankshaft of the exhaust cam for opening and closing an exhaust valve, is changed between a predetermined most advanced value and a predetermined most retarded value as a supply hydraulic pressure from the exhaust side hydraulic control valve is changed. In this case, when the intake cam phase is set to the most advanced value and the exhaust cam phase is set to the most retarded value, a valve overlap period of the intake valve and the exhaust valve becomes maximum.
In this control apparatus, during normal control, the intake cam phase and the exhaust cam phase are controlled to respective optimum values by controlling the variable intake cam phase mechanism and the variable exhaust cam phase mechanism, and if there has occurred a state where foreign matter is caught in one of the intake-side and exhaust-side hydraulic control valves, there are performed foreign matter removal control of the one of the intake-side and exhaust-side hydraulic control valves in which the foreign matter is caught, and phase maintaining control of the other of the hydraulic control valves. For example, if there has occurred a state where foreign matter is caught in the exhaust-side hydraulic control valve, there are performed exhaust-side foreign matter removal control of the exhaust-side hydraulic control valve and intake-side phase maintaining control of the intake-side hydraulic control valve.
In the exhaust-side foreign matter removal control, a spool valve of the exhaust-side hydraulic control valve is driven such that the spool valve repeats reciprocating motion between a position where the exhaust cam phase is set to most advanced value and a position where the exhaust cam phase is set to most retarded value, by controlling a duty ratio of a control input signal supplied to the exhaust-side hydraulic control valve such that it is repeatedly inverted between 0% and 100%. This resolves the state of the foreign matter being caught in the exhaust-side hydraulic control valve. Further, in the intake-side phase maintaining control, the intake-side hydraulic control valve is controlled such that the intake cam phase is maintained at a predetermined value α which is slightly advanced with respect to the most retarded value.